1. Field of the Invention
The invention relates to indicating a multi-slot channel in a TDMA radio system, in which the radio channel normally consists of one timeslot in frames made up of several successive timeslots.
2. Description of the Prior Art
In TDMA radio systems, such as many current digital cellular mobile communication systems, the radio channel is normally assigned to one timeslot in frames transmitted at radio frequency, made up of several successive timeslots. Current TDMA mobile communication systems and their radio terminals have been devised so as to enable traffic channels and control channels of various types to be formed in them. For instance in a GSM system, channels of various types, such as a traffic channel and an associated control channel, may share the capacity of the same timeslot. Some systems already allow more than one channel to be allocated at the same time. The GSM system also allows simultaneous assignment of two "half rate" traffic channels. As new services have been developed, it has turned out that, in order to achieve higher transmission capacity on a radio channel, TDMA radio systems and their radio terminals should preferably be designed to allow multi-slot channels to be readily formed and used. The present invention is specifically concerned with accomplishing this potential improvement.
EP patent specification A2 399 611 discloses a solution relating to the improvement indicated above, describing a system for rapidly assigning several duplex speech channels to a radio terminal with a view to gain higher data speed in data message transmission from the radio terminal. The basic idea of the system described is that the terminal keeps record of the use and the quality of the duplex speech channels. and whenever necessary, any additional speech channels required are directly assigned for data message transmission on the basis of the data in this record. The radio terminal may also utilize data provided by the base station and the system control unit about the availability of the speech channels, and in this conjunction, the paging or speech forming message provided by the base station may include data about the number of duplex speech channels required and/or about the numerals of the suggested channels. However, this system basically does not allow for assignment of successive physical channels. The configuration of this specification is characterised by including special provisions for swiftly making several speech channels available for rapid data transmission. The specification mentions signalling only in passing, stating that guidance data about the number of channels required and suggestions for channels to be assigned can be signalled to the radio terminal, the general impression being that this is also extra signalling for additional data transmission, apart from normal operation. In contrast. the purpose of the present invention is specifically to provide for signalling in the assignment of a multi-slot channel without increasing or complicating the signalling compared to normal operation.